Adding GetEventSource() method to the WindowTreeHost class.

ui/aura/window_tree_host_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/aura/window_tree_host_win.h"
 
 #include <windows.h>
 
 #include <algorithm>
 
@@ skipping 37 matching lines @@
   SetWindowText(hwnd(), L"aura::RootWindow!");
   CreateCompositor(GetAcceleratedWidget());
 }
 
 WindowTreeHostWin::~WindowTreeHostWin() {
   DestroyCompositor();
   DestroyDispatcher();
   DestroyWindow(hwnd());
 }
 
+ui::EventSource* WindowTreeHostWin::GetEventSource() {
+  return this;
+}
+
 gfx::AcceleratedWidget WindowTreeHostWin::GetAcceleratedWidget() {
   return hwnd();
 }
 
 void WindowTreeHostWin::Show() {
   ShowWindow(hwnd(), SW_SHOWNORMAL);
 }
 
 void WindowTreeHostWin::Hide() {
   NOTIMPLEMENTED();
@@ skipping 175 matching lines @@
 namespace test {
 
 // static
 void SetUsePopupAsRootWindowForTest(bool use) {
   use_popup_as_root_window_for_test = use;
 }
 
 }  // namespace test
 
 }  // namespace aura